PURPOSE: To provide a gear angle regulating mechanism in which a back lash can be prevented, the gear angle can be regulated in an accurate value, no unreasonable force is applied to the component parts, and an excellent durability is provided, in a gear angle regulating mechanism used for a mounting apparatus of electronic parts.

CONSTITUTION: A driving gear 28 is driven to rotate by a driving shaft 32, a flexible coupling 34 is installed to the driving shaft 32, and the driving gear 28 is pressed in the direction of driven gears 8 by a compression spring 28. By fluctuating a driving arm 26 around an arm shaft 16 as the center, the engagement and its release of the driving gear 28 and the driven gears 8 are made possible. The driven gears 8 are combined to an adsorption nozzle 4 of electronic parts, and by the rotation of the driven gears 8, the rotating angle of the adsorption nozzle 4 can be regulated. In such a constitution, the back lash of the driving gear and the driven gears can be made almost 0. As a result, the rotating position of the adsorption nozzle can be regulated accurately.